DirectBufferAllocTest fails after replacement of Thread.sleep() with Thread.onSpinWait()

[Alan Bateman]

On 20/06/2022 22:58, David Holmes wrote:
>
> Thread.onSpinWait _is_ busy-waiting, but it may (depending on 
> architecture) actually execute a more (power) efficient form of 
> busy-wait.
>
> The takeaway from this exercise is that loops with sleeps can't always 
> be replaced by loops that busy-wait. Functionally the logic is the 
> same, but you can't just ignore the concurrency aspects.
Right, and in this case I don't think a busy wait would be very 
efficient as it would require a very high max spin count. To date 
Peter's exponential back-off has worked well and it's rare to hear about 
OOME cases caused by code that that is allocating direct buffers for 
single use. In time, I assume we will see more code using the new FFM 
API which can support deterministic memory release.

-Alan